Adult moose mortality project

Complexities abound

Minnesota moose are some tough critters but research is showing that complex factors are combining to make their survival more and more precarious.

Just how tough are moose? And how complex can the situation become for the largest member of the deer family? Consider Moose 192, a 12-year old cow that DNR researchers collared in 2015 and died in April along a Superior National Forest road not too far west of Finland.

Twelve years is a relatively old age for a moose yet she was healthy enough to become fertile, be bred and carry a healthy male fetus to term.

That's an accomplishment for a healthy moose but Moose 192 did this while suffering from three serious health problems:

A winter tick infestation causing major hair loss and anemia from blood loss

A liver fluke infection, one of the worst encountered so far in the study, that weakens moose and predisposes them to other illness

The presence of brainworm, severe infections of which cause circling, weakness in the hindquarters, inability to stand, turning of the neck and head to one side, lethargy, apparent blindness, loss of fear and rapid eye movement.

Despite these conditions, the cow settled down in late April to give birth. While calving, which made her extremely vulnerable, wolves attacked and inflicted massive injuries to her head and rump.

Moose 192 fought off her attackers though and, with her bull calf still in the birth canal, wandered about 1,000 yards north and laid down in a watery ditch along the roadside, tucking her front legs underneath. She likely drew her last breaths when under water as she and her unborn calf died.

The mortality study will consider Moose 192's official cause of death to be wolf kill. But facts gathered from the GPS collar and results of the necropsy show that this moose endured serious health conditions. Calving – not sickness – made her vulnerable to a wolf attack. But it's likely that health conditions eventually would have killed her.

Closeup of a puncture wound from a wolf bite in Moose 192's jaw.

Moose 192, a 12-year-old pregnant cow, fought off wolves while giving birth. After the attack she walked about 1,000 feet before laying down and dying in a watery ditch.

Loggers reported that a nine-month-old male moose calf was walking in circles, standing in open areas and unafraid of people. The team euthanized the animal and test results confirmed a brainworm infection.

Survial rate

The annual adult moose survival rate for 2016, the fourth year of the study, is 95 percent so far. Annual survival rates in previous years were:

85 percent in 2015

88 percent in 2014

81 percent in 2013

The chart below provides an overview of all moose deaths in the study to date. Clicking an individual chart will display that chart's complete detail.

Causes of adult moose mortalities

February 2013 - June 2016 (n=49)

Moose 192 report

Moose 192, a 12-year-old pregnant cow, fought off wolves while giving birth. After the attack she walked about 1,000 feet before laying down and dying in a watery ditch.

Moose 192, a 12-year old cow that DNR researchers collared in 2015, died in April along a Superior National Forest road not too far west of Finland.

Necropsy results showed three serious health problems:

A winter tick infestation causing major hair loss and anemia from blood loss

A liver fluke infection, one of the worst encountered so far in the study, that weakens moose and predisposes them to other illness

The presence of brainworm, severe infections of which cause circling, weakness in the hindquarters, inability to stand, turning of the neck and head to one side, lethargy, apparent blindness, loss of fear and rapid eye movement.

Despite these conditions, the cow settled down in late April to give birth to a healthy bull calf. While calving, which made her extremely vulnerable, wolves attacked and inflicted massive injuries to her head and rump.

Moose 192 fought off her attackers though and, with her bull calf still in the birth canal, wandered about 1,000 yards north and laid down in a watery ditch along the roadside, tucking her front legs underneath. She likely drew her last breaths when under water as she and her unborn calf died.

The mortality study will consider Moose 192's official cause of death to be wolf kill. But facts gathered from the GPS collar and results of the necropsy show that this moose endured serious health conditions. Calving – not sickness – made her vulnerable to a wolf attack. But it's likely that health conditions eventually would have killed her.

Moose 21 report

Winter ticks on Moose 21, a nine-year-old bull that died of the infestation.

An alert from the collar of Moose 21, a nine-year-old bull collared in 2013, sent the retrieval team to an alive but unable to stand animal on April 28. In fact, the moose didn't even try to move when the team arrived.

The moose was euthanized and a field necropsy was performed because the moose had sought shelter in dense cover, making extraction of the carcass impossible.

A severe winter tick infestation was apparent. There was significant hair loss and the animal was covered in ticks. The bull was emaciated and all his organs were pale, a condition caused by severe anemia.

Examination of organ samples done later in the lab revealed the moose also had meningitis in the brain and may have suffered from a mild brainworm infection.

Sickness caused by the winter tick infestation was the primary cause of death.

Moose 205 report

Moose 205 dead in the snow.

The mortality implant transmitter and collar on this six-year-old bull, which was collared in 2015, sent alerts at 7 a.m. on Thursday, Jan. 7. By 1:30 p.m., the crew had located the carcass. The moose had shed its antlers and was skinny before it laid down; it appeared to have collapsed where it laid.

Using snowmobiles and a special folding sled, crew members retrieved the entire carcass and hauled it the University of Minnesota laboratory by pickup truck that evening.

Retrieval crew members load Moose 205 into the bed of a pickup truck.

Necropsy results showed an emaciated animal with a weight of only 795 pounds. Bone marrow in its femur was red and jelly like, indicating that the moose was starving and its body had consumed its last source of remaining fat from its bone marrow.

The exam also revealed that the moose had a severe case of hepatitis, which had been induced by liver flukes. Infectious bacteria were isolated from the liver and lungs and the abdomen was inflamed. The bacterial infection, caused by liver fluke induced hepatitis, was the primary cause of death.